With the rapid development of mobile phone technologies, a mobile phone increasingly includes more functions, for example, a camera may be integrated on the mobile phone so that the mobile phone has a camera function.
Referring to FIG. 1, when a user uses a camera function included in a mobile phone to take an image, if the user needs to vary a focal length of a camera of the mobile phone, the user can use two fingers of one hand to make a stretch or pinch gesture on a touch screen of the mobile phone, so as to vary the focal length of the camera of the mobile phone. For example, two fingers of the user make a stretch gesture on the touch screen to lengthen the focal length of the camera of the mobile phone, or make a pinch gesture on the touch screen to shorten the focal length of the camera of the mobile phone. Assuming that the user makes a stretch gesture on a touch screen shown in FIG. 1 to lengthen the focal length of the camera of the mobile phone, an image taken by the camera of the mobile phone and shown in FIG. 1 is zoomed in as an image shown in FIG. 2.
Currently, the user at least uses one hand to hold the mobile phone to take images, and needs to use the other hand alone to make a stretch or pinch gesture on the touch screen of the mobile phone to vary the focal length of the camera of the mobile phone, which has poor operation convenience.